1. Field of the Invention
This invention relates to a method for the heat treatment, at temperature above 1200.degree. C., of semiconductor components which are introduced into a quartz-glass tube, a gas stream being conducted through the quartz-glass tube. More especially, this invention simply relates to a manner of maintaining quartz-glass tubes at temperatures above 1200.degree. C. to avoid a deformation of the tubes when they are at temperatures above 1200.degree. C.
2. Discussion of the Prior Art
The use of quartz-glass tubes has long been known for the fabrication of semiconductor components, as, for example, for the purpose of diffusing doping agent into silicon wafers or of depositing doped epitaxial layers on silicon wafers. It has been found that at the elevated temperatures employed the quartz-glass tubes used undergo very considerable plastic deformation. As a result, the racks carrying the semiconductor wafers no longer fit into the quartz-glass tube, which means that the deformed quartz-glass tubes must frequently be replaced with new, underformed tubes.
With a view to overcome this drawback of deleterious deformation, German Pat. No. 1,771,077 discloses quartz-glass tubes intended for use in semiconductor fabricating processes and provided on their external surface with a coating formed by a cohesive, finely crystalline cristobaslite layer. Quartz-glass tubes of this type have proven themselves for many years. However, the manufacture of such quartz-glass tubes requires an additional heat treatment of regular quartz-glass tubes.
In view of the drawback of deformation of quartz-glass tubes, it has also been proposed to use silicon or silicon carbide tubes in their place. (German Auslegsschrift DAS 23 53 411.)